The present invention relates to an optical recording/reproduction device whereby information is optically recorded on a recording medium by using a light beam from a laser or the like, or recorded information is reproduced.
In a conventional optical recording/reproducing device, tracking control is performed by using a tracking actuator to move a focusing lens in the radial direction of the recording medium. Such a tracking actuator consists of a fixed section and a movable section on which is mounted the focusing lens, the fixed section and mobile section being coupled by means of four wires (linear members) or a resilient element such as a rubber element. When current is passed to a coil provided in the movable section, electromagnetic force is generated between it and a permanent magnet provided in the fixed section, causing the focusing lens to be moved by this electromagnetic force in the radial direction of the recording medium i.e. the direction perpendicular to the tracks.
Searching of a track containing desired information is performed by moving the entire optical head including the tracking actuator in the radial direction of the recording medium and counting the number of tracks on the recording medium that are crossed by the light beam. When, during searching, the optical head is moved at high speed in the radial direction of the recording medium, the focusing lens is subjected to inertial force, causing it to vibrate. In the conventional device, a speed sensor was provided that detected the speed of movement of the optical head, the signal of the speed sensor being differentiated to obtain an acceleration signal; the inertial force was cancelled by applying this acceleration signal to the tracking actuator, thereby reducing the vibration of the focusing lens (for example, Japanese Patent Laid-Open Publication No. Sho. 58-166567).
The prior art optical recording/reproducing device was subject to the problem that, since a speed sensor was required in order to reduce vibration of the tracking actuator during searching, the weight of the movable section of the optical head was increased, with the result that considerable power was required in order to perform fast searching. A further problem was that miniaturization of the optical head was difficult because of the speed sensor.
The present invention was made having regard to the above problems of the prior art. Its object is to provide an optical recording/reproducing device wherein swinging of the focusing lens during searching can be suppressed and high tracking pull-in performance ensured, and, in addition, which has fast and stable searching performance at low cost, thanks to controlling the speed of movement of the focusing lens during searching even under fluctuation of the drive sensitivity of the tracking actuator and traverse motor resulting from changes over time or temperature variation.
Furthermore, since, if the tracking capability of the traverse motor during tracking control is poor, feed control is performed with the focusing lens always in a displaced condition, with the result that very poor tracking jumps occur, an object is to provide an optical recording/reproduction device wherein the tracking capability of the traverse motor is improved and that provides high-precision feed control.
The present invention consists in a device for recording information onto a recording medium or reproducing recorded information comprising:
means for projecting a light beam that focus and project a light beam onto a recording medium;
first means for movement that move the means for projecting a light beam by a minute amount in a direction practically perpendicular to a track on the recording medium;
means for detecting track error that generate a signal corresponding to the positional relationship of the light beam and a track;
means for controlling tracking that drive the first means for movement in response to a signal of said means for detecting track error and that exercise control such that the light beam scans the track;
second means for movement that move the light beam crosswise in a direction approximately perpendicular to the track on the recording medium by moving the means for projecting a light beam; and
means for controlling searching that move the light beam across a plurality of tracks to a desired track; wherein the means for controlling searching comprise:
means for generating a target speed that generate a target speed for movement of the light beam;
means for detecting speed of movement that detect the speed of movement of the light beam;
first means for driving that drive the first means for movement in response to a difference signal of a signal of the means for generating a target speed and a signal of the means for detecting speed of movement; and
second means for driving that drive second means for movement in response to a difference signal of a signal of the means for generating a target speed and a signal of the means for detecting speed of movement.